Chair manufacturers continually strive to improve the comfort, benefits, aesthetics, and manufacturability of the chairs they produce. Often, chairs have features, such as a reclining back, to increase comfort. Sometimes, chairs have features, such as adjustable seats, backs, back supports, armrests, and heights, to reduce or prevent injuries, including repetitive stress injury and back pain associated with sitting for long periods. Chairs are designed and built to fill an individual's needs and provide support where the individual needs it. In some chairs, the seat and back are fixed or the seat is fixed and the back tilts for comfort. In other chairs, the seat and back move together to support the user.